Pilot burners are used in gas turbine engines to ignite a fuel/air mixture, in particular to ignite a mixture of liquid fuel and/or gas fuel with air, in the burning zone, which is directed afterwards the pilot burner, i.e. downstream. The fuel and the air are mixed together in a swirling zone and are ignited in the burning zone of the pilot burner to create a high-energy fluid flow to propel a turbine section of the gas turbine engine.
Current designs of burner are made of austenitic stainless steel, which possesses good resistance to scaling at high temperatures and which can be used for continuous high temperature operation. Austenitic stainless steel is a compromise material to keep the costs of the pilot burner down and to provide good resistance to the temperature.
But because of the excessive stresses induced by the temperature gradients during engine operation this design of pilot burner, in particular of the pilot burner face, is susceptible to cracking and thereby reducing pilot burner life.
Therefore it is known to provide the face of the pilot burner with a MCrAlY coating to reduce oxidation attack and to keep the metal temperature in the pilot burner within acceptable limits for component life. MCrAlY is an acronym for a composition of metal (“M” stands for Ni, Co, or Fe base or mixtures thereof), Chromium (“Cr”), Aluminum (“Al”), and Yttrium (“Y”).
But the coating on a pilot burner face has some disadvantages. The coating is often not thick enough to give a good protection from high temperatures, especially over a long time.